An AC surface-discharge panel, a typical plasma display panel (abbreviated as “panel” hereinafter) has a large number of discharge cells formed between the front and back panels arranged mutually facing. The front panel has plural display electrode pairs, each composed of a pair of scan electrode and sustain electrode, formed parallel to one another on the front glass substrate, and has a dielectric layer and protective layer formed so as to cover the display electrode pairs. The back panel has plural, parallel data electrodes on the back glass substrate, a dielectric layer so as to cover the data electrodes, plural barrier ribs parallel to the data electrodes over the dielectric layer, and a phosphor layer on the top surface of the dielectric layer and on the side surface of the ribs, respectively formed. The front and back panels are arranged mutually facing so that a display electrode pair crosses a data electrode at different levels, and sealed. The internal discharge space is encapsulated with a discharge gas containing xenon by 5% in partial pressure, for example. Here, discharge cells are formed between a display electrode pair and data electrode mutually facing. In a panel with such a structure, ultraviolet light is generated in each discharge cell by means of gas discharge. The ultraviolet light excites phosphors for red (R), green (G) and blue (B) to cause light emission for color display.
One of general methods of driving a panel is subfield method, where a single field period is divided into plural subfields before gradation display is made by means of a combination of subfields made emit light. Each subfield has a initialization period, writing period, and sustain period. In the initialization period, initializing discharge is generated to form wall charge required for the subsequent writing operation on each electrode. In the writing period, writing discharge is generated selectively at a discharge cell to display to form wall charge. Then in the sustain period, sustain pulses are alternately applied to a display electrode pair composed of a scan electrode and a sustain electrode; and sustain discharge is generated at a discharge cell that caused writing discharge to make a corresponding discharge cell emit light for image display.
Another new method of driving a panel among subfield methods is disclosed. That is, initializing discharge is performed using a voltage waveform gently changing, selectively for a discharge cell that performed sustain discharge to reduce light emission not related to gradation display to a minimum level for improving the contrast ratio.
Specifically, in the initialization period of one subfield out of plural subfields, all-cell initializing operation is performed that makes all the discharge cells discharge, and in the initialization period of the other subfields, selective initialization is performed that initializes only discharge cells that have performed sustain discharge. Consequently, light emitting not related to display results in only light emitting accompanying discharge for all-cell initializing operation, enabling image display with a high contrast (refer to patent literature 1, for example).
Thus driving a panel makes the luminance of the black display region changing depending on light emitting not related to image display to be caused only by feeble light emitting in all-cell initializing operation, enabling image display with high contrast.
However, a panel has been increasingly enlarged in screen size as well as providing higher resolution in recent years, making writing discharge unstable. Consequently, writing discharge fails to occur in a discharge cell where display must be performed, thus deteriorating the quality of image display or increasing voltage required for stably generating writing discharge.
[Patent literature 1] Japanese Patent Unexamined Publication No. 2000-242224